Share This

STANFORD, Calif. - One of the unfortunate side effects of bone marrow and stem cell transplantation is that the newly implanted cells often stage an internal attack against the patient they're intended to help. Stanford University School of Medicine researchers now have a better grasp of this phenomenon, known as graft-versus-host disease, or GVHD, and have proposed a possible method of prevention: simple ultraviolet light.

Related Articles

In a new animal study, researchers identified the principal culprit in GVHD: an immune cell in the skin known as a Langerhans cell. These cells normally function as flag posts for the immune system, signaling infection-fighting T-cells to come to a particular site to fight off a virus or bacteria. But in transplants, they do patients a great disservice, alerting T-cells to attack the patient's own tissues, researchers found.

The researchers were able to effectively eliminate the Langerhans cells in transplanted mice by exposing them to ultraviolet light, giving the animals mild sunburn. Transplanted mice that received this treatment experienced no GVHD while those that didn't showed severe signs of the disease, said Edgar Engleman, MD, professor of pathology and medicine and senior author of the study.

"The experiment not only provided the proof that these cells cause graft-versus-host disease, but also provides a way of thinking about how you might prevent it," said Engleman, who also directs the Stanford Blood Center. The study appears in the May issue of the journal Nature Medicine.

Bone marrow or stem cell transplants are commonly used to treat patients with cancers of the blood system, such as leukemia, lymphoma or myeloma. Patients first receive radiation treatment to wipe out their defective immune systems, which then are replaced by healthy donor cells.

Sometimes, however, the process fails as GVHD sets in. The effects of the disease are most commonly seen in the skin as a reddish rash or, in more severe cases, as skin that blisters and peels.

The Stanford scientists first suspected that Langerhans cells might have a major role in GVHD after their earlier experiments showed these cells were resistant to radiation and persisted in the skin for a long time, said Miriam Merad, MD, PhD, a former postdoctoral scholar in Engelman's lab and the first author of the study. The discovery was "shocking," Engleman said, as all other white blood cells have a short half-life and are frequently replaced. The Langerhans cells don't change unless they're disturbed in some way, say by inflammation, he said.

The scientists surmised that these cells might linger in the skin of a transplant patient and instigate trouble. Their latest experiments bore this out.

The researchers tested their theory in two different sets of mice. In one group, the animals had their own Langerhans cells intact. When these animals were transplanted, the Langerhans cells triggered a response and the mice developed severe GVHD. In a second group, the scientists replaced the animals' Langerhans cells with other cells. When these mice underwent transplant, they remained protected from GVHD.

The scientists took it a step further. They exposed the vulnerable mice - those with their own Langerhans cells - to ultraviolet light using a sunlamp. The sun exposure depleted the Langerhans cells and effectively protected the mice from the disease, said Merad, who is now based at the Mount Sinai School of Medicine.

The researchers said the results present a promising option for transplant patients and could be the basis for clinical trials in which patients are exposed to ultraviolet light before treatment.

"What we would do is try to eliminate the host Langerhans cells before the transplant, as we did in the mice," Merad said. She noted that dermatologists now use ultraviolet light to treat some skin diseases, administering it to patients inside a chamber under controlled circumstances to avoid burning.

Engleman said the ultraviolet treatment would have to be carefully administered to patients before bone marrow or stem cell transplantation to avoid harmful side effects. "The trick is deplete the host Langerhans cells in a manner that doesn't cause other unwanted effects," he said.

The study was funded by the National Institutes of Health and by a grant from the Irene Diamond Fund.

Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu.

More From ScienceDaily

More Health & Medicine News

Featured Research

Mar. 3, 2015 — Scientists have discovered a new hormone that fights the weight gain caused by a high-fat Western diet and normalizes the metabolism -- effects commonly associated with exercising. When tested in ... full story

Mar. 3, 2015 — New assays can detect malaria parasites in human blood at very low levels and might be helpful in the campaign to eradicate malaria, reports a new study. An international team led by Ingrid Felger, ... full story

Mar. 3, 2015 — Adults over the age of 30 only catch flu about twice a decade, a new study suggests. So, while it may feel like more, flu-like illness can be caused by many pathogens, making it difficult to assess ... full story

Mar. 3, 2015 — No significant change in home habits of smokers have been observed in the aftermath of a ban on smoking in public spaces, researchers report. Greater inspiration to kick the habit likely comes from ... full story

Mar. 3, 2015 — Heart function has been associated with the development of dementia and Alzheimer's disease through a new study. Participants with decreased heart function, measured by cardiac index, were two to ... full story

Mar. 3, 2015 — Children of recently separated or divorced families are likelier to drink sugar-sweetened beverages than children in families where the parents are married, putting them at higher risk for obesity ... full story

Mar. 3, 2015 — Gastric bypass and similar stomach-shrinking surgeries are a popular option for obese patients looking to lose weight or treat type 2 diabetes. While the surgeries have been linked to a decreased ... full story

Mar. 3, 2015 — Most people consume more salt than they need and therefore have a higher risk of heart disease and stroke, which are the two leading causes of death worldwide. But a new study reveals that dietary ... full story

Featured Videos

Mom Triumphs Over Tragedy, Helps Other Families

AP (Mar. 3, 2015) — After her son, Dax, died from a rare form of leukemia, Julie Locke decided to give back to the doctors at St. Jude Children&apos;s Research Hospital who tried to save his life. She raised $1.6M to help other patients and their families. (March 3)
Video provided by AP

Looted and Leaking, South Sudan's Oil Wells Pose Health Risk

AFP (Mar. 3, 2015) — Thick black puddles and a looted, leaking ruin are all that remain of the Thar Jath oil treatment facility, once a crucial part of South Sudan&apos;s mainstay industry. Duration: 01:13
Video provided by AFP

Woman Convicted of Poisoning Son

AP (Mar. 3, 2015) — A woman who blogged for years about her son&apos;s constant health woes was convicted Monday of poisoning him to death by force-feeding heavy concentrations of sodium through his stomach tube. (March 3)
Video provided by AP

Related Stories

Nov. 18, 2014 — A genetic test that identifies patients at high risk of kidney transplant rejection has been developed by researchers. About 20% of kidney transplants are rejected by the patient, they say, and ... full story

Aug. 7, 2013 — Researchers have identified and validated a biomarker accessible in blood tests that could be used to predict which stem cell transplant patients are at highest risk for a potentially fatal immune ... full story

Apr. 1, 2012 — A new discovery in mice may lead to new treatments that could make bone marrow transplants more likely to succeed and to be significantly less dangerous. Scientists may have found a way to prevent ... full story

May 18, 2011 — Researchers have discovered a method to quickly and exponentially grow regulatory T-cells -- also known as "suppressor cells." The new process enables replication of the cells by tens of ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.